Modern systems often employ detection of certain events to initiate or ‘trigger’ one or more actions or reactions by the system. These so-called ‘trigger events’ may include, for example, a change in local environment or a change in a characteristic of a signal monitored by the system. For example, oscilloscopes have long employed triggers based on characteristics of an input signal to synchronize or coordinate measurements performed by the oscilloscope. In an analog oscilloscope, a rising or falling edge of an input signal may be used to synchronize a display sweep to facilitate displaying the input signal in a vicinity of the rising or falling edge, for example. With the advent of digital systems and more particularly digital data acquisition systems such as, but not limited to, digital oscilloscopes, the synchronization or coordination has been naturally extended to include one or both of starting and stopping the acquisition of data based on the occurrence of a particular trigger event. Starting and/or stopping data acquisition according to a trigger event may be used to ensure that a portion of the input signal around the trigger event is present in the data acquired, for example.
In early digital versions of various data acquisition systems, analog trigger event detection, often derived directly from an analog version of the data acquisition system, may have been employed. However, there has been a general trend toward replacing analog trigger event detection with digital trigger event detection in modern systems to overcome some of the inherent limitations of using analog-based trigger event detection.